281是从2开时的第几个质数2算第一个3第二个5第三个7第四个……

Question

281是从2开时的第几个质数
2算第一个
3第二个
5第三个
7第四个
……

Answer 1

前100个素数：2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523……
很明显281是第60个,你最好再数一数